The present disclosure relates to cryogenic pumps and more particularly, to processes, apparatuses, and kits for assembling cryogenic pumps.
Cryogenic liquids such as hydrogen, oxygen, nitrogen, argon, liquefied hydrocarbons (e.g., methane, natural gas), and the like, are normally stored in well-insulated, temperature-controlled containers, such as underground storage tanks, to reduce fluid evaporation losses. The cryogenic temperatures of these liquids are generally considered to range from about 125° Kelvin (K) to 0° K.
To transfer such cryogenic fluids between containers or from one container to a point of use, reciprocating- or centrifugal-type mechanical pumps are often employed. These types of cryogenic pumps basically consist of a vertically extending column having an intake, and one or more stages of impellers mounted about a shaft at the lower end of the column. The impellers are driven by the shaft, which extends coaxially upward through the column to a drive motor mounted on top of a discharge head, which is mounted on top of the vertical column. During operation, the pump intake is located at the bottom of the pump and is submerged into the cryogenic liquid. Rotation of the impellers causes the liquid to be drawn into the pump intake and to an outlet conduit in fluid communication with another container, a conduit, or its point of use. Depending upon the particular application, these pumps are normally of substantial size with typical column lengths of about 15 to about 20 feet or more, and column diameters ranging up to about 3 feet or more. The cryogenic pump is thus made up of several major components, each of which may weigh several hundred pounds, wherein the total weight of the cryogenic pump can be in excess of about 10,000 to about 20,000 pounds or more.
Assembly or disassembly of cryogenic pumps is relatively complicated. Many of the components are extremely bulky, and require precise coaxial alignment of separable parts. A drive shaft of about 18 to about 20 feet in length or larger which, in operation, will be driven at several hundred to thousands of revolutions per minute (rpm), must be installed with some degree of precision. Current assembly and disassembly processes include vertically assembling or disassembling the various components that form the cryogenic pump.
FIG. 1 (A–L) illustrates one such prior art process for vertically assembling or disassembling a cryogenic pump. The vertical assembly process typically requires building a special pit area 12 to accommodate the diameter of the pump and staging for use by the assemblers. The pit area 12 is necessary to accommodate a portion of the pump height as it is being assembled as well as for safety considerations associated with vertically stacking the various components to assemble the pump. For example, a suitable pit area for fabricating an 18-foot long cryogenic pump weighing about 8500 pounds is about 4 feet in width, 10 feet in length, and about 9 feet deep. As shown in FIG. 1A, the motor and shaft assembly components 16 are first lowered into the pit area 12 and positioned onto a telescoping workstand 14 located at the bottom of the pit area 12. The motor and shaft assembly 16 are oriented “upside down” and are typically disposed in the pit area 12 by means of an overhead crane, fork truck fitted with an overhead boon, a combination of the crane and fork truck, or the like. Additional component modules 18, 20, 22 of the pump are each then vertically fitted to the motor and shaft assembly 16 in a similar manner as shown in FIG. 1B. Fitting the additional component modules require the assemblers to be able to freely move up and down the staging to access the pump for guiding, mating, and attaching the various component modules as the cryogenic pump is assembled. With regard to the one or more stages of impellers, each impeller as it is fitted to the shaft is offset from the previously fitted impeller by about 30 to about 90 degrees. The orientation of each additional impeller is maintained due to the effect of gravity as the impeller blades are being fitted to the shaft.
Referring now to FIGS. 1D through 1H, once all of the major component modules 16, 18, 20, and 22 of the pump are assembled, it is necessary to rotate the entire pump assembly 180 degrees, such that the pump is in its normal operating position, i.e., the motor and shaft assembly 16 is positioned at the top of the pump 10, the impellers at the bottom of the pump. Again, an overhead crane, fork truck, or the like, is required for rotating the assembled pump into the normal operating position within the pit area 12. Final connections and assembly of secondary or minor components are then made by an assembler to complete the cryogenic pump as shown in FIG. 1I. Referring now to FIGS. 1J through 1L, the pump is now readied for testing, which involves transporting the cryogenic pump to a testing facility for connection to a container of cryogenic liquid, wherein it will be installed in the vertically oriented, normal operating position.
Once the pump has been tested, the cryogenic pump is typically brought back to the pit area 12 for disassembly. Disassembly is required to determine wear patterns and to replace any pump components damaged during testing. The pumps are then reassembled and readied for shipment to the customer. Typically, a cryogenic pump will be assembled, tested, disassembled, and reassembled two or three times prior to shipment to a customer site.
The vertical assembly process is time intensive requiring frequent interaction with overhead cranes, fork trucks with overhead boons, and the like, for assembly, disassembly, and for orienting the pump for testing purposes. Moreover, the known cryogenic pump assembly processes require the use of a special pit area 12 and staging for access to the pump as it is assembled in the vertical direction.